Two Russian-built Kilo submarines cruise the dark, frigid waters of the North Sea out of Kaliningrad, being readied for delivery later this year to Vietnam, where Indian technicians are already helping to train Vietnamese crews.

Down in the Philippines, meanwhile, final preparations are under way to seal a deal to buy a squadron of jet fighters from South Korea and receive three naval helicopters from Italy.

As Southeast Asia's military build-up intensifies to counter China's military rise, it is increasingly clear that it has an international dimension, tying China's neighbours to a widening range of relationships that could complicate Beijing's strategic environment.

"There is certainly a strong international component to these developments in Southeast Asia," said Richard Bitzinger, a senior fellow at Singapore's S. Rajaratnam School of International Studies, who is tracking a growing list of acquisitions across the region. "Southeast Asia is a very open arms market compared to other parts of the world like the Middle East … there is no shortage of potential sellers, and plenty of interested buyers.

"And in this business, you don't want to be dependent on any one supplier, so that explains all the shopping around. Price is, of course, another factor."

Vietnam has long attempted to diversify its sources as it rebuilds its once-formidable military, reflecting a marked internationalist cast to its foreign policy, avoiding alliances and over- reliance on any one major actor.

Hanoi has looked to Moscow - its cold war-era patron - for key elements of its state-of-the-art kit, including frigates and Sukhoi jet fighters, as well as the Kilos. But it is also tapping India for anti-ship cruise missiles and talking to various European nations, including France, for ships and radars and has lobbied Washington hard about lifting restrictions on weapons sales - a legacy of the Vietnam war.

One representative of a major US weapons manufacturer said there was considerable US interest in potential business from Vietnam, but State Department officials have told them they must wait for improvements in the Communist Party-ruled nation's human rights situation.

For the Philippines, however, its move into the international arms market is something new - and a factor that is surprising analysts. A US ally tied to Washington by a decades-old security treaty, Philippines' leaders have long ignored calls to update its tiny and creaking armed forces, relying on the occasional infusion of surplus US materiel.

President Benigno Aquino is determined to challenge that perception, pushing ahead with bold plans to gradually increase defence spending after years of atrophy. The US$443 million deal to buy the South Korean FA-50 light fighter jets will give the Philippines its first meaningful air attack capability in the best part of two decades. The planes are also a perfect training platform for more advanced F-16s from the US – another deal in the frame.

The jet purchase is being matched by other moves, including buying 10 coastguard ships from Japan under an aid deal, and talks with a host of other nations about possible purchases. The significance of a Russian naval task force visit to Manila Bay a year ago - the first such mission in 96 years - was not lost on military analysts.

"The amazing thing is not just that they are buying from a range of countries, but it is amazing that they are buying at all," Bitzinger said.

And then there is Indonesia. Southeast Asia's largest nation has been active as well, purchasing submarines from South Korea, anti-ship missiles from China, Sukhoi jets from Russia and F-16s from the US.

Bitzinger noted that Indonesian defence spending rose 200 per cent in the decade to 2010, reaching US$6 billion and boosting regional figures that saw spending across Southeast Asia rise more than 50 per cent during the same period.

The trend looks set to expand. Bitzinger said he expected Indonesia, Vietnam and possibly oil-rich Brunei to significantly increase defence spending, with Indonesia overtaking traditional military heavyweight Singapore as the biggest player.

Officially, of course, it is not targeted at China. As Aquino spokesman Edwin Lacierda said last week: "The military upgrade was already a priority before our incident with China … It is not aimed at any particular country. It is our obligation to modernise our military hardware."

But speak privately with military brass and strategists across the region and the spectre of China's vaunted military ambitions - fuelled by two decades of double-digit spending rises - looms large. Vietnam and the Philippines, of course, are locked in increasingly tense territorial disputes over the South China Sea, along with fellow claimants Malaysia and Brunei. Philippine officials have described their sovereignty as being under direct threat as Chinese ships maintain a permanent presence in the disputed Scarborough Shoal, within the Philippines' claimed exclusive economic zone.

Given the reach of China's controversial "nine-dash line" claim deep into the maritime heart of Southeast Asia, countries such as Singapore and Indonesia look on nervously.

"No one of us is ever going to be in a position to challenge China militarily," one Vietnamese strategist said. "What we can do is create a strategic deterrent that would make them think very long and hard before contemplating even a limited conflict to enforce their claims. That's what we are doing … as well as reminding China now and then that we would be prepared to fight to defend our sovereignty."

Vietnam's dynamic deputy defence minister, Lieutenant General Nguyen Chi Vinh, has already stated, in a clear nod to China, that if any party escalated the dispute, "we would not stand by and watch".

While Vietnam is well on the way to such a position, the Philippines still has a long way to go, as the Scarborough Shoal situation suggests. In creating that deterrent, countries are effectively trying to do to China what China is trying to do to the US, whose military remains the most powerful in the wider Asian region.

Through the use of so-called asymmetric weapons such as a submarines and anti-ship missiles, a larger foe can be deterred - as China hopes the US would be in case of a conflict over Taiwan

Professor Carl Thayer, who has been monitoring the build-up at the Australian Defence Force Academy, recently described it as a "cycle of action-reaction", driven in large part by China's military rise and assertiveness. It is not about ultimate supremacy, so it can not be seen as a classic arms race.

"But neither Vietnam nor Indonesia are straining their economic resources to develop their armed forces," he said. "And to both Vietnam and Indonesia, China creates a security dilemma but it is not an adversary."

Major international weapons manufacturers and exporters have been increasingly active across the region, appearing behind the scenes at high-profile gatherings such as the informal Shangri-La Dialogue in Singapore, an annual gathering of defence ministers, top military brass and scholars.

"In the last year or so, I've noticed the smiles on the faces of my peers working the region are getting broader, and their cigars bigger," said one regional representative of a large US weapons and systems manufacturer.

"It's nice to be in a growth industry."

This article appeared in the South China Morning Post print edition as for war